Cold press bonded semi-conductor housing joint



March 6, 1962 H. c. NIJHUIS ETAL COLD PRESS BONDED SEMI-CONDUCTORHOUSING JOINT Filed March 26, 1958 SEMI-C DEVICE FIGJ WWW/WWW INVENTORHERMAN CORNELIS NIJHUIS WILHELMUS ANTONIUS ROOVERS AGEN United StatesPatent Ofiice 3,024,299 Patented Mar. 6, 1962 3,024,299 COLD PRESSBONDED SEMI-CONDUCTOR HOUSING JOINT Herman Cornelis Nijhuis andWilhelmus Antonius Roovers, Mollenhutseweg, Nijmegen, Netherlands, as-

signors to North American Philips Company, Inc., New

York, N.Y., a corporation of Delaware Filed Mar. 26, 1958, Ser. No.725,774 Claims priority, application Netherlands Apr. 16, 1957 6 Claims.(Cl. 174-50.5)

This invention relates to a semi-conductor electrode system or device,for example a transistor or a crystal diode, provided with avacuum-tight envelope made substantially of metal.

It has already been proposed for such an envelope to be constituted byat least two parts, facing surfaces of these parts being united togetherby pressure. In this device, one press surface consisted of acomparatively hard metal and another engaging press surface consisted ofa comparatively soft metal, the surface made of the harder metal beingprovided with at least one groove the lateral walls of which were atsubstantially right angles to the said surface, while this groove orthese grooves was or were filled with the softer metal.

These suggestions referred substantially to combinations of parts thesofter of which consisted of metals such as copper and aluminum and theharder of iron and steel. In many semi-conductor electrode systems theheat dissipation is important and in this respect envelope parts made ofiron or steel have a limitation in that they have a comparatively highthermal resistance.

It is an object of the present invention to provide a construction inwhich the envelope can be made substantially entirely from soft metalsof good thermal conductivity, such as copper and aluminum.

According to the invention, the envelope comprises at least two partsprovided with facing press surfaces, grooves being formed in thesesurfaces the walls of which are substantially at right angles to thesaid surfaces, while between these surfaces there is interposed a layerof very soft metal which fills the grooves, one of the said two partshaving a flanged rim which embraces the other part and presses and keepsthe parts together. The term very soft metal is to be understood to meana metal the hardness of which is less than 25 V.P.N. (Vickers PyramidalNumber). In a preferred embodiment, the press surface of one part liesin a recess of the other part, a rim of this recess being designed as aflanged rim.

In order that the invention may readily be carried out, two embodimentsthereof will now be described by way of example, with reference to theaccompanying drawings, the two figures of which each are cross-sectionalviews of a transistor or a crystal diode, the semi-conductor bodies withthe electrodes and the lead-in conductors being shown in block form forthe sake of simplicity.

The envelope shown in FIG. 1 comprises a base 1 and a cover 2. The base1 is provided with a press surface located in a recess 3 in its rimconstituting a flanged portion; in this recess, there is formed a groove4 having substantially vertical walls. The cover 2 is provided with aflange 5 the lower side of which forms a press surface in which a groove6 is formed. Between the two press surfaces there is interposed in therecess 3 a layer 7 consisting of a very soft metal, such as lead, tin orindium, for example in the shape of a ring. The layer may also beproduced by melting a soft metal in the recess so that it spreads.Subsequently, the base 1 is laid on a table, there being arranged on theflange 5 of the cover a ram by which the press surfaces are pressedtogether with such pressure that the grooves 4 and 6 are entirely filledwith the soft metal. Furthermore,

preferably during the application of this pressure, a flanged rim 8 madefrom the rim of the recess 3 is pressed over the flange 5 so that theparts 1 and 2 are hermetically joined together.

The envelope shown in FIG. 2 comprises a base 11 and a cover 12. Twogrooves 13 are formed along the rim of the base 11. The cover 12 has aflange 14 in which two grooves 15 have also been formed. The parts ofbase and cover in which these grooves are formed again constitute thepress surfaces between which a layer 16 of a very soft metal isinterposed. These press surfaces have again been pressed together with ahigh pressure, a flanged rim 17 of the cover 12 being subsequentlyfolded over the base 11.

These constructions have the advantage that the layers of soft metal 7and 16 may consist of a metal having a very slight mechanical strength;this layer ensures the vacuum-tight seal but the flanged rims 8 and 17ensure the mechanical closure of the envelope.

An attendant advantage consists in that the base 1 or 11 and the cover 2or 12 may be made of substantially any metal which otherwise fulfillsthe requirements to be satisfied by such envelopes. Both iron and copperor brass have proved highly suitable.

The provisions of the grooves 4, 6 and 13, 15 respectively has provednecessary for ensuring a vacuum-tight seal.

What is claimed is:

1. A semi-conductor device comprising a semi-conductive element, and avacuum-tight, cold-pressed, metal envelope enclosing said element, saidenvelope comprising two metal members having outwardly-extending flangedportions with facing surface portions, each of said surface portionscontaining a groove whose walls are substantially at right angles totheir respective surface portion, a separate layer of a very soft metaldisposed completely between and cold-press-bonded to both of the facingsurface portions and filling both grooves in the surface portions andforming a vacuum-tight bond to and between the metal members, said metalmembers at the facing surface portions being substantially undeformed bythe bonding operation, and a further flanged portion of and integralwith one of said metal members embracing a portion of the other memberand permanently mechanically joining and holding them together.

2. A device as set forth in claim 1 wherein one of the metal members isflat, and the other is cup-shaped with a flanged bottom.

3. A semi-conductor device comprising a semi-conductive element, and avacuum-tight, cold-pressed, metal envelope enclosing said element, saidenvelope comprising two thermally-conductive metal members, one of saidmetal members comprising a flat base member having an annular recessalong its rim, the other metal member comprising a cup-shaped memberwith a flanged bottom portion seated in the recess and defining with thebottom wall thereof facing surface portions, each of said surfaceportions containing a groove, which opposes the groove in the othersurface portion, whose walls are substantially at right angles to theirrespective surface portion, a separate annular layer of a very softmetal disposed in the recess completely between and cold-press-bonded toboth of the facing surface portions and filling both grooves in thesurface portions and forming a vacuum-tight bond to and between themetal members, said metal members at the facing surface portions beingsubstantially undeformed by the bonding operation, and a further flangedportion of and integral with one of said metal members embracing aportion of the other member and permanently mechanically joining andholding them together.

4. A device as set forth in claim 3 wherein a corner portion definingthe recess in the base member is flangedover and embraces the flangedbottom of the cup-shaped member.

5. A semi-conductor device comprising a semi-conductive element, and avacuum-tight, cold-pressed, metal envelope enclosing said element, saidenvelope comprising two metal members having outwardly-extending flangedportions with facing surface portions, said metal members being of softthermally-conductive metal, each of said surface portions containing agroove whose walls are substantially at right angles to their respectivesurface portion, said grooves being opposed to one another, a separatelayer of a very soft metal disposed completely between andcold-press-bonded to both of the facing surface portions and fillingboth grooves in the surface portions and forming a vacuum-tight bond toand between the metal members, said metal members at the facing surfaceportions being substantially undeformed by the bonding operation, and afurther flanged portion of and integral with one of the said membersembracing a portion of the other member and permanently mechanicallyjoining and holding them together.

6. A device as set forth in claim 5 wherein both metal members are ofcopper.

References Cited in the file of this patent FOREIGN PATENTS

